Nafpaktos (Greek: Ναύπακτος) is today a town and a former municipality in Aetolia-Acarnania, West Greece, Greece; its predecessor in the classical period is known in English as Naupactus. Nafpaktos is situated on a bay on the north coast of the Gulf of Corinth, 3 km (2 mi) west of the mouth of the river Mornos. The harbour is accessible only to the smallest craft. It is 9 km (6 mi) northeast of Antirrio, 18 km (11 mi) northeast of Patras, 35 km (22 mi) east of Missolonghi and 45 km (28 mi) southeast of Agrinio. The Greek National Road 48/E65 (Antirrio - Nafpaktos - Delphi - Livadeia) passes north of the town. It is the second largest town of Aetolia-Acarnania, after Agrinio.
The 1571 Battle of Lepanto, in which the navy of the Ottoman Empire was decisively defeated by the Holy League assembled by Pope Pius V, is named for Naupactus under the Italian form of its name.
Since the 2011 local government reform, it has been part of the municipality of Nafpaktia
, of which it is the seat and a municipal unit.